Apple states that the spring layer consists of an array of metal springs, embedded within which are force-sensing structures such as strain gauges. Additionally, the patent suggests that if necessary, foam columns and other compressible structures can be interspersed with the springs to help adjust the performance of the spring layer.
Various flexible metals can be used for the spring layer, including spring steel, nickel-chromium-aluminum alloys, beryllium copper alloys, stainless steel, cobalt-nickel alloys, and other spring metals. Attached below are relevant images from pulsestacks:
Apple stated that introducing a spring layer into foldable screen devices can alleviate external pressure from impacts and compression events, while also mitigating stress on the screen during repeated folding and unfolding, thus enhancing the durability of foldable screen devices.
Apple believes that this spring layer can alleviate external pressure and prevent excessive localized deformation.
via: patentlyapple
